Many of the portable electronic apparatuses are requested to have slim designs. So, loudspeakers built in such apparatuses are also required to have slim designs as well.
A generally practiced way of making conventional loudspeakers thinner is reducing the size of magnet which forms magnetic circuit; such as the one described in the Patent Document 1 below. The smaller-sized magnet can provide the smaller magnetic force; as the results, the sound output shrinks. Therefore, the magnet size can not be reduced very much, so that the efforts for thickness reduction with conventional loudspeakers have not yielded significant achievements.
There is another approach for improving the disadvantage due to size reduction of magnet; that is splitting a magnet into pieces and placing the split pieces of the magnet at appropriate locations. However, placing those magnetized pieces precisely at specific locations is a difficult job because each one exhibits magnetic attracting force or repelling force.
Patent Document: Japanese Patent Unexamined Publication No. 2005-51283.